Cyclophanes are a subset of organic structures that are well known and characterized. Several excellent reviews and books have been published that cover the methods and applications very well.
Briefly, cyclophanes and other related benzocycloid compounds are organic molecules that have structures where a cyclic carbon or heteroatom substituted chain is attached to two or more positions of an aromatic ring. The term cyclophanes is used to describe compounds that have a relationship or a structure that broadly fits into this structural category.
One of the more highly researched cyclophane compounds is the paracyclophane structure. In one set of cyclophane compounds (as shown in the structures of [n]metacyclophanes (I), [n]paracyclophanes (II) and [n,n′]cyclophanes below), we see structure III as a general structure for paracyclophanes.

In this substitution pattern we note that the simplest member of the series is where n=1. In this case the molecule is named [2,2′]paracyclophane. This molecule and derivatives thereof are an important class of compounds that are able to form a variety of polymer structures. For this reason they are highly desirable organic intermediates that have been used as precursors for conformal coatings for numerous applications. In these applications the molecule shown in III (n=1) is normally heated in a vacuum to produce a significant vapor pressure and to force a disassociation of the molecule into a highly reactive intermediate. This pyrolytic cleavage of the [2.2°]paracyclophane results in two molecules of the reactive intermediate p-xylylene (shown below).

Additionally, the reactive intermediate p-xylylene may be formed from the “dimer” by utilization of a pyrolysis discharge under reduced atmospheric pressure. (ref. Gorham U.S. Pat. No. 3,342,754). This procedure has commonly been called the “Gorham process”.
As the structure indicated, the reactive intermediate, p-xylylene is a long-lived intermediate species that has the ability to react to form a highly desirable polymer. In particular this polymer is a conformal coating that has the ability to coat surfaces in relatively uniform layers that are highly resistant to chemical solvents, gases, and biological attack. The p-xylylene is deposited in a vacuum onto a target surface for conformal coating. On the surface it reforms into a repeating unit of poly(p-xylylene), also known as parylene. In the case of no substituents in the aromatic ring or the aliphatic side-chains other than hydrogen, this polymer compound is called parylene-N.

Para-xylylene, as a valuable reactive intermediate, has had its synthesis primarily through the pyrolysis of [2,2′]paracylophane. Thus, the synthesis of [2,2′]paracyclophane is a critical stable intermediate in the utilization of p-xylylene and the polymer parylene.
Synthesis of [2,2′]paracylophane is through the route of the 1,6-Hofmann elimination of quaternary ammonium salts.

This route going through a quaternary ammonium salt, although widely used, suffers from several drawbacks. The paracylophane is usually produced in low yields using a multi-step processes.
Additionally, due to the low yield and large amount of side-products, extensive purification of the resultant dimer is an additional process procedure.